1. Field of the Invention
The present invention relates to an optical apparatus, such as a camera having a function to adjust the diopter, which can correct the diopter, taking characteristics of photographer's eye into account.
2. Related Background Art
There is an apparatus which detects the refractivity of the eye of a photographer and automatically corrects the diopter of the apparatus, based on a value of the detection.
Such an apparatus, however, uses an eye refractometer provided as detecting means for detecting the amount of correction of the diopter, in a finder, which causes the following problems.
(1) The eye refractometer is very expensive because the refractometer requires a high-luminance LED, a special coating on its lens, and a high-precision photo sensor for detecting a position.
(2) Diopter adjustment with an eye refractometer consumes a lot of energy and has a long setting time. Since accurate diopter detection cannot be made unless the measurement by the eye refractometer is continued throughout the period of taking a picture, the emission time of the high-luminance LED becomes longer, which increases dissipation power. Also, because the position for correcting the diopter is determined while accommodation of the person and diopter adjustment by a mechanical drive are alternately repeated, some time is necessary for completely correcting the diopter and excessive energy is dissipated for driving the lens.
(3) When the eye refractometer is set inside a camera it is difficult to obtain high accuracy. Since the reflectivity at the retina is as low as 0.2% incident light from unnecessary portions (ghosts) becomes problematic for detection. However, different from eye refractometers for exclusive use as refractometers, the finder is set near an eyepiece portion, where incident light from the outside is inevitable (particularly, in the case of wearers of glasses, where the influence of external incident light is great because of the long distance between the eyepiece portion and the eye). It is thus difficult to perfectly remove ghosts. Also, because the external light is incident directly into the eye, the diameter of the pupil becomes narrower when the outside is bright, thereby making accurate measurement of eye refractivity difficult.